Saturday’s technical malfunction at Balti substation did not pose risk to integral operation of Estonian power system

Saturday’s malfunction in the Elering-managed Balti substation in Ida-Viru County was caused by a failure of a current transformer and probably also by a fire that broke out as a result of an internal short-circuit.

“The incident was exceptional. The 330-kilovolt transformers at Balti substation should not have shut down due to the failure of the current transformer. The substations and the power system as a whole are built so that a fault in an individual piece of equipment shouldn’t leave consumers in the dark. If anything happens to one system component, the computers should automatically transfer the power supply to another component – to backup equipment. An event like the one that occurred at Balti substation that left consumers without power has not happened before in the 10 years that I have been at the helm of Elering. Yet the fault did not pose a risk to the operation of the Estonian electrical system as a whole," said the chairman of the Elering management board Taavi Veskimägi.

“Elering currently does not know why Eesti Energia’s power generating equipment shut down, and we intend to ask Eesti Energia for additional information on this. The production equipment that, as we were told by Eesti Energia, switched off was not connected to the Balti substation but rather to Viru substation, which was not affected by Saturday’s failure. Eesti Energia’s production equipment at Eesti Power Plant shut down after the malfunction at Elering’s Balti substation was already resolved. According to rules in force in Estonia, all power plants connected to the grid should be able to stay online in the case of such a malfunction. If other electricity production equipment connected to normally functioning substations shuts down, this causes problems for the TSO in controlling the system and it raises the question of whether the equipment that shut down meets valid Estonian requirements,“ added Veskimägi.

Saturday’s shutdown affects consumers of the regional distribution grid VKG Elektrivõrgud. VKG Elektrivõrgud operates in Narva, Narva-Jõesuu and Sillamäe. The overwhelming majority of consumers got their power back from Elering about an hour after the outage started.

As one of the main indicators for the company, Elering keeps track of the operating reliability of the power grid. The operating reliability of the Elering grid has improved in leaps and bounds in recent years. Last year, Elering’ s grid experience 86 outages, which resulted in only 18.5 megawatt-hours of electricity not being transmitted – that’s about the same amount as the annual consumption for two households.